horns, defense, and rutting

[Tom Holtz <tholtz@geochange.er.usgs.gov>]

>He was firmly of the opinion that the horns
>were more or less strictly for combat amongst each other (is
>intraspecific the right term here?), pointing out that one's head was
>probably the worst place one would want a defensive weapon - if a
>Triceratops would be lucky enough to gore a Tyrannosaurus, it would then
>face the problem of several tons of opponent causing stress on its neck,
>either thrashing or collapsing.

Intraspecific combat is the correct term, and a lot of evidence does
indicate that that was the primary use of the horns in the male morphotype.
Chasmosaurine [aka ceratopsine] ceratopsids like Triceratops, Torosaurus,
etc., come in two adult morphologies:  one form where the horns are
directed primarily forward, one where they are more upwardly directed.
Lehman and others have suggested that the forward projecting forms were
males, because such a morphology allows the horns to lock together between
opponents to aloow for a shoving match.  The more upwardly directed forms
(the females?) may have used their horns more for decoration and/or
defense, since they would not lock together as well.

>I'm not sure about his argument - don't deer and buffalo use their horns
>as defense against wolves, as well as for rutting?  Anyone know anything
>about horns used against significantly larger predators? (like maybe
>antelope or gazelle versus big cats?)

Indeed, most horned mammals do use their equipment in interspecific defense
as well as intraspecific rivalry (there's the old classic Disney footage of
a white-tailed deer charging a puma).  The presence of horns in and of
themselves are useful for defense against predators; the different shapes
of horns are mostly related to species-specific (redundant!) behaviors.

                                
Thomas R. Holtz, Jr.                                   
tholtz@geochange.er.usgs.gov
Vertebrate Paleontologist in Exile                  Phone:      703-648-5280
U.S. Geological Survey                                FAX:      703-648-5420
Branch of Paleontology & Stratigraphy
MS 970 National Center
Reston, VA  22092
U.S.A.